Mayor Walter E. Washington has nominated six persons to serve as trustees of the University of the District of Columbia, including the present chairman, who was chosen for a second term.

The new nominees include the head of the city's largest bank and a former D.C. school teacher.

All the nominations are for five-year terms on the 15-member board and are subject to confirmation by the City Council. The board of trustees is the university government body.

Of the nominees, three are from Ward 3 and one from Ward 4 on Northwest Washington, and one is from Ward 7 in Southeast.

The only incumbent, nominated for a second term, is Ronald Brown, currently chairman of the board trustees, who works in the Washington office of the National Urban League.

The mayor's nimination does not automatically mean Brown will remain as chairman, since the board elects it own officers.

The other nominees are:

Kenneth M. Crosby, resident vice president of Merrill, Lynch, Pierce, Fenner and Smith, who is active in numerous civic organizations. He would replace Richard K. Fox Jr., who resigned.

Thomas W.D. Wright, and architect who has been active in housing matters and was on the advisory council of the Washington Technical Institute, a predecessor of UDC. He would succeed Bryant G. Harris, whose term expires.

Daniel J. Callahan III, president of Riggs National Bank, a native Washington who serves on several business and civic organizations. He would succeed Brenda Lee Belton, whose term expires.

Nira Hardon Long, a lawyer in private practice who has been active in women's black and civil liberties organizations. She would succeed Dr. Benjamin J. Henley, current vice chairman of the board of trustees, whose terms expires.

Elba M. Martinez, acting director of information for the Puerto Rican government office in Washington and a former teacher at two D.C. high schools. She would succeed Armando B. Rendon, whose term expires.

Mayor Washington also nominated Aulander Stevenson as one of the three landlord representatives on the nine-member Rental Accommodations Commission. He would succeed Flaxie Pinkett, who resigned recently.

A real estate broker, Stevenson served until earlier this year as senior property manager for Pinkett's real estate firm, John R. Pinkett Inc. The commission sets policies for the city's rent control program and hears appeals from administrative officials on rent levels.

The City Council also recently confirmed three nominations by the mayor to the Commission on the Arts and Humanities and renominations to the Zoning Commission and the Commission of Aging.

Approved for the arts board were W. Robert Lomax and Elva Chaplin Wells, both serving first terms, and Anthony Taylor, who was approved for a second term.

The Zoning Commission member is Ruby Burrows McZier, an attorney who has served on that body since 1975.

The council confirmed the Rev. Dr. Lowell R. Ditzen for a second term on the Commission on Aging.

On Tuesday, the council confirmed the nomination of Ruth Hankins-Nesbitt for a second three-year term on the Public Service Commission. She currently chairs the commission, which chooses its own officers.